We discuss the spin evolution of pulsars in the case where a superfluid component of the star is coupled to the observable crust on long , spindown timescales .
The momentum transfer from the superfluid interior results in an apparent decay of the external torque and , after a dramatic increase , to an asymptotic decrease of the generic value of the braking index , e.g . n = 3 , to values n \sim 2.5 if the magnetic field of the star does not decay over its lifetime .
In the case where an exponential decay of the magnetic field towards a residual value occurs , the star undergoes a spin-up phase after which it could emerge in the millisecond sector of the P - \dot { P } diagram .